1. Field of the Invention
The present invention relates to damping devices for electric circuit breakers, and in particular for gas insulated high voltage circuit breakers of the so-called puffer-type.
2. Prior Art
In connection with electric circuit breakers it is previously known to use damping devices of the type which comprises a housing filled with a damping liquid and comprising a displaceably arranged damping cylinder, in which a piston which is connectible to the movable contact of a circuit breaker is displaceable between a first and a second end position corresponding to the closed and open positions, respectively, of the circuit breaker. The piston limits two cylinder spaces positioned on opposite sides of the piston and having restricted outlet openings. Damping devices of this type have been described, for example, in the German Patent Specifications Nos. 706,622 and 914,026.
When breaking a great current with a puffer-type SF.sub.6 circuit breaker, a high pressure is generated in the puffer cylinder during the latter stage of the opening movement by the arc in the circuit breaker partially blocking the gas flow path. This high pressure causes a counter force which may for a brief period exceed the driving force of the operating mechanism. The counter force results in the opening movement being slowed down. In extreme cases the breaker movement may become reversed. Such a reversal of the opening movement reduces the breaking capacity of the circuit breaker very considerably by causing the pressure in the puffer cylinder to become low.